Ceramic or ceramic matrix composite (CMC) materials may be useful in a variety of contexts where mechanical and thermal properties are important. For example, components of high temperature mechanical systems, such as gas turbine engines, may be made from ceramic or CMCs. Ceramic or CMC materials may be useful in high temperature environments, but some ceramics or CMCs may react with some elements and compounds present in the operating environment of high temperature mechanical systems, such as water vapor. Reaction with water vapor may result in the recession of the ceramic or CMC substrate. These reactions may damage the ceramic or CMC and reduce mechanical properties of the ceramic or CMC, which may reduce the useful life of the component. In some examples, a ceramic or CMC substrate may be coated with an environmental barrier coating, which may reduce exposure of the substrate to elements and compounds present in the operating environment of high temperature mechanical systems.